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tmux

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tmux

tmux (Terminal Multiplexer) lets you run multiple terminal sessions in one window, detach and reattach them, split panes, and share sessions between users. It’s essential for remote work, long-running processes, and working across multiple tasks simultaneously.

Sessions, Windows, Panes

tmux hierarchy:
  Session    → tmux new -s mysession
    Window   → Ctrl+b c
      Pane   → Ctrl+b %  (vertical split)
                Ctrl+b "  (horizontal split)
  • Session: a persistent running environment
  • Window: like a terminal tab (one per task/workflow)
  • Pane: split view within a window

Core Commands

# Start tmux (new session, default naming)
tmux
 
# New named session
tmux new -s webserver
 
# Attach to existing session
tmux attach -t webserver
tmux attach          # attach to last session
 
# List sessions
tmux ls
tmux list-sessions
 
# Detach from session
Ctrl+b d
 
# Kill session
tmux kill-session -t webserver
 
# Kill all tmux
tmux kill-server

Key Bindings (Prefix = Ctrl+b)

ActionKey
Send prefixCtrl+b
New windowCtrl+b c
Next windowCtrl+b n
Previous windowCtrl+b p
List windowsCtrl+b w
Rename windowCtrl+b ,
Kill windowCtrl+b &
Split verticalCtrl+b %
Split horizontalCtrl+b "
Switch paneCtrl+b arrow
Cycle paneCtrl+b o
Swap panesCtrl+b { Ctrl+b }
Zoom paneCtrl+b z
Kill paneCtrl+b x
DetachCtrl+b d
Command promptCtrl+b :

Panes Deep Dive

# Split current pane horizontally
Ctrl+b "
 
# Split current pane vertically
Ctrl+b %
 
# Switch to pane by direction
Ctrl+b arrow-key
 
# Cycle through panes
Ctrl+b o
 
# Swap pane with next/prev
Ctrl+b }
Ctrl+b {
 
# Make pane full screen (zoom)
Ctrl+b z
# Repeat to un-zoom
 
# Convert pane to window
Ctrl+b !
 
# Break pane into window
Ctrl+b : break-pane
 
# Join window into pane
Ctrl+b : join-pane -s -t mywindow
 
# Resize pane (hold Ctrl+b, then arrow)
Ctrl+b : resize-pane -D 10   # resize down 10
Ctrl+b : resize-pane -U 5    # resize up 5
Ctrl+b : resize-pane -L 20   # resize left 20
Ctrl+b : resize-pane -R 20   # resize right 20

Copy Mode (Scrolling, Searching)

# Enter copy mode
Ctrl+b [
 
# Navigation in copy mode
# Arrow keys or vim-style:
h j k l         # left/down/up/right
Ctrl+b          # page up
Space           # start selection
Enter           # copy selection and exit
q               # exit copy mode
 
# Search
Ctrl+b /         # search forward
?               # search backward (in copy mode)
 
# Copy to clipboard (if using set-clipboard):
# In tmux 3.0+:
set -g set-clipboard on
# Then in copy mode: select text, Enter to copy, Ctrl+v to paste in any app

Vim-style pane navigation

# Add to ~/.tmux.conf for vim-style pane switching:
cat >> ~/.tmux.conf << 'EOF'
# Vim-style pane navigation
bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R
 
# Mouse support (optional)
set -g mouse on
 
# Longer prefix escape delay (fixes Esc delay in vim)
set -g escape-time 0
EOF
 
tmux source-file ~/.tmux.conf

Status Bar

# Current status bar config:
tmux show-options -g status
 
# Example custom status bar:
set -g status-bg colour235
set -g status-fg colour255
set -g status-left "#[fg=green]#S #[fg=blue]»"
set -g status-right "#[fg=blue]%Y-%m-%d %H:%M"
set -g status-right-length 50
set -g window-status-format "#I:#W"
set -g window-status-current-format "#[fg=cyan,bold]#I:#W"
 
# Show activity in other windows:
setw -g monitor-activity on
set -g visual-activity off

Synchronize Panes

# Type in all panes simultaneously (e.g., run same command on multiple servers)
Ctrl+b :
set synchronize-panes on
# Now everything you type goes to all panes
# Repeat to disable:
set synchronize-panes off
 
# Practical use: tail logs on multiple servers
# Split into 4 panes, SSH to each, then sync

Scripts and Automation

Send commands to a session from outside

# Run command in session (detached)
tmux send-keys -t webserver 'cd /var/log' Enter
tmux send-keys -t webserver 'tail -f nginx/access.log' Enter
 
# Run full shell script in pane
tmux send-keys -t webserver 'bash -c "ls -la"' Enter
 
# Capture pane output to file
tmux capture-pane -t webserver:0.1 -p > /tmp/pane-output.txt
 
# List all panes:
tmux list-panes -t webserver

tmux in scripts (non-interactive)

# Create session if it doesn't exist
tmux new-session -d -s deploy -c /home/darshan/projects
 
# Split into panes and run commands
tmux split-window -h -t deploy
tmux send-keys -t deploy:0.0 'cd /home/darshan/projects && git pull' Enter
tmux send-keys -t deploy:0.1 'docker-compose up -d' Enter
 
# Wait for command to finish:
tmux send-keys -t deploy:0.0 'make build' Enter
tmux pipe-pane -t deploy:0.0 -t /tmp/build.log
 
# Attach when done:
tmux attach -t deploy

Multi-session startup script

#!/bin/bash
# ~/.local/bin/tmux-startup
 
SESSION="work"
 
# Create if doesn't exist
tmux new-session -d -s "$SESSION" -c ~/projects
 
# Window 1: editor
tmux new-window -t "$SESSION:1" -n vim -c ~/projects
tmux send-keys -t "$SESSION:1" 'nvim' Enter
 
# Window 2: servers
tmux new-window -t "$SESSION:2" -n servers -c ~/projects
tmux split-window -h -t "$SESSION:2"
tmux send-keys -t "$SESSION:2.0" 'ssh server1' Enter
tmux send-keys -t "$SESSION:2.1" 'ssh server2' Enter
 
# Window 3: monitoring
tmux new-window -t "$SESSION:3" -n logs -c /var/log
tmux send-keys -t "$SESSION:3" 'htop' Enter
 
# Attach
tmux attach -t "$SESSION"

Useful Options

# ~/.tmux.conf — commonly useful settings
 
# Enable mouse (click to select, resize panes)
set -g mouse on
 
# Start window numbering at 1 (not 0)
set -g base-index 1
setw -g pane-base-index 1
 
# Renumber windows when one is closed
set -g renumber-windows on
 
# Don't rename windows automatically
set -g allow-rename off
 
# Set terminal colors
set -g default-terminal "tmux-256color"
set -g default-terminal "screen-256color"
 
# Faster key repeat
set -g repeat-time 500
 
# History limit
set -g history-limit 50000
 
# Focus events (for vim inside tmux)
set -g focus-events on
 
# Reload config
bind r source-file ~/.tmux.conf \; display "Config reloaded"

Sessions across SSH

# On remote server:
ssh server
tmux new -s work
 
# Detach (Ctrl+b d), logout
 
# Later, SSH back and reattach:
ssh server
tmux attach -t work
 
# Or directly attach without creating new:
ssh -t server 'tmux attach'

Share Session (Pair Programming)

# User A:
tmux -S /tmp/shared new -s pair
chmod 777 /tmp/shared
 
# User B:
tmux -S /tmp/shared attach
 
# Both see the same terminal. Anything either types appears to both.
# Warning: both have full control.

Quick Reference

# Basics
tmux new -s name              # new session
tmux attach -t name            # attach
tmux ls                        # list sessions
Ctrl+b d                       # detach
 
# Panes
Ctrl+b %                       # vertical split
Ctrl+b "                       # horizontal split
Ctrl+b arrow                   # navigate panes
Ctrl+b z                       # zoom pane
 
# Windows
Ctrl+b c                       # new window
Ctrl+b n/p                     # next/prev window
Ctrl+b w                       # list windows
Ctrl+b ,                       # rename window
 
# Copy mode
Ctrl+b [                       # enter copy mode
q                             # exit copy mode
Space                          # start selection
Enter                          # copy
 
# Scripts
tmux send-keys -t session 'cmd' Enter   # send command
tmux capture-pane -t session:0.0 -p    # capture output
tmux pipe-pane -t session:0.0 -t log   # log pane to file

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